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windfarm_cpufreq_clamp.c

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/wait.h>
#include <linux/cpufreq.h>

#include <asm/prom.h>

#include "windfarm.h"

#define VERSION "0.3"

static int clamped;
static struct wf_control *clamp_control;

static int clamp_notifier_call(struct notifier_block *self,
                         unsigned long event, void *data)
{
      struct cpufreq_policy *p = data;
      unsigned long max_freq;

      if (event != CPUFREQ_ADJUST)
            return 0;

      max_freq = clamped ? (p->cpuinfo.min_freq) : (p->cpuinfo.max_freq);
      cpufreq_verify_within_limits(p, 0, max_freq);

      return 0;
}

static struct notifier_block clamp_notifier = {
      .notifier_call = clamp_notifier_call,
};

static int clamp_set(struct wf_control *ct, s32 value)
{
      if (value)
            printk(KERN_INFO "windfarm: Clamping CPU frequency to "
                   "minimum !\n");
      else
            printk(KERN_INFO "windfarm: CPU frequency unclamped !\n");
      clamped = value;
      cpufreq_update_policy(0);
      return 0;
}

static int clamp_get(struct wf_control *ct, s32 *value)
{
      *value = clamped;
      return 0;
}

static s32 clamp_min(struct wf_control *ct)
{
      return 0;
}

static s32 clamp_max(struct wf_control *ct)
{
      return 1;
}

static struct wf_control_ops clamp_ops = {
      .set_value  = clamp_set,
      .get_value  = clamp_get,
      .get_min    = clamp_min,
      .get_max    = clamp_max,
      .owner            = THIS_MODULE,
};

static int __init wf_cpufreq_clamp_init(void)
{
      struct wf_control *clamp;

      /* Don't register on old machines that use therm_pm72 for now */
      if (machine_is_compatible("PowerMac7,2") ||
          machine_is_compatible("PowerMac7,3") ||
          machine_is_compatible("RackMac3,1"))
            return -ENODEV;

      clamp = kmalloc(sizeof(struct wf_control), GFP_KERNEL);
      if (clamp == NULL)
            return -ENOMEM;
      cpufreq_register_notifier(&clamp_notifier, CPUFREQ_POLICY_NOTIFIER);
      clamp->ops = &clamp_ops;
      clamp->name = "cpufreq-clamp";
      if (wf_register_control(clamp))
            goto fail;
      clamp_control = clamp;
      return 0;
 fail:
      kfree(clamp);
      return -ENODEV;
}

static void __exit wf_cpufreq_clamp_exit(void)
{
      if (clamp_control)
            wf_unregister_control(clamp_control);
}


module_init(wf_cpufreq_clamp_init);
module_exit(wf_cpufreq_clamp_exit);

MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
MODULE_DESCRIPTION("CPU frequency clamp for PowerMacs thermal control");
MODULE_LICENSE("GPL");


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